DS90LV027A_16 Datasheet, PDF (13/21 Pages) Texas Instruments – LVDS Dual High Speed Differential Driver

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DS90LV027A
SNLS026D – MARCH 2000 – REVISED JUNE 2016
Typical Application (continued)
9.2.2 Detailed Design Procedure
9.2.2.1 Probing LVDS Transmission Lines
Always use high impedance (>100 kΩ), low capacitance (<2 pF) scope probes with a wide bandwidth (1 GHz)
scope. Improper probing gives deceiving results.
A pseudo-random bit sequence (PRBS) of 2⁹−1 bits was programmed into a function generator (Tektronix
HFS9009) and connected to the driver inputs through 50-Ω cables and SMB connectors. An oscilloscope
(Tektronix 11801B) was used to probe the resulting eye pattern, measured differentially at the input to the
receiver. A 100-Ω resistor was used to terminate the pair at the far end of the cable. The measurements were
taken at the far end of the cable, at the input of the receiver, and used for the jitter analysis for Figure 21. The
frequency of the input signal was increased until the measured jitter (ttcs) equaled 20% with respect to the unit
interval (ttui) for the particular cable length under test. Twenty percent jitter is a reasonable place to start with
many system designs. The data used was NRZ. Jitter was measured at the 0-V differential voltage of the
differential eye pattern.
The DS90LV027A and DS90LV028A can be evaluated using the new DS90LV047-048AEVM.
9.2.3 Application Curves
Figure 20. Power Supply Current
vs Frequency
Figure 21. Data Rate
vs Cable Length
10 Power Supply Recommendations
Although the DS90LV027A draws very little power while at rest, at higher switching frequencies there is a
dynamic current component which increases the overall power consumption. The DS90LV027A power supply
connection must take this additional current consumption into consideration for maximum power requirements.
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